The present invention relates to thread-guiding components of a facility for the production, treatment and processing of fiber materials with a surface coming into contact with said fiber materials or their raw materials and whose properties change only little in continuous operation over a prolonged period of time and which therefore, in comparison with corresponding conventional components, have a considerably improved service life.
In the production of synthetic fibers numerous components are used which come into close contact with the spun, fast-moving threads while having to fulfill various functions. Examples of such components are bundling and deflecting devices, which are intended to combine the plurality of filaments or change the path direction of filament bundles, snubbing pins, which have to define the stretching point of filament paths, take-off godets, i.e. rolls which haul off the plurality of threads from the spinneret, drawing godets, between which the filament bundles are drawn and thereby oriented and consolidated, intermingling jets, in which the filament bundles passing through are intermingled by blown-in compressed air in order that the textile effect of the threads and the holding-together of the individual filaments of the threads (yarn adhesion) may be improved. Depending on the type of duty, the filaments come into contact with the components slidingly, as in the case of deflecting devices or intermingling Jets, or they are to come into contact with the components in more or less positive or at least frictional form, as in the case of take-off or drawing godets, or in sliding contact, in which case, however, defined forces are to be transmitted, as in the case for example of snubbing pins.
It has long been known that the quality of threads obtained is in large measure dependent on the flawless quality of the surfaces of these components and that changes in the surface in the course of continuous operation lead after a certain period of operation ("service life") to a considerable increase in the faults in the fiber material produced, making it necessary to replace the component. The replacement of the component is costly, since there is not only the expense of a new or reconditioned component but production has to be interrupted for a certain period of time, which incurs considerable additional costs.
It has therefore long been customary to manufacture such thread-guiding components from very wear-resistant materials which retain a defined surface over a long period of operation so as to ensure very long service lives. A source of particularly frequent problems are the godets, which serve to convey the fiber materials. They must on the one hand be able to apply to the fiber materials going around them a high tensile force, which requires a positive, or at least frictional, contact, but they must not tend to bind the individual filaments too strongly, since these are otherwise torn from the fiber bundle and form problem wraps on the godet. Such godets are therefore expected to have a very advantageous grip-release behavior. Filament breakages, however, impair not only the production process but also represent quality defects, which can lead to serious difficulties in the further processing of the threads.
Widely used are godets whose surface comprises a ceramic material, preferably a ceramic mixture of Al.sub.2 O.sub.3 with from 3 to 20% by weight of TiO.sub.2, in particular with about 13% by weight of TiO.sub.2. These standard godets can be used in both feed and take-off systems and make it possible to obtain an at least practicable degree of sustained operation from a spinning machine. However, even with these godets the service life is not all that may be desired; especially the service lives vary randomly from godet to godet and, what is more, this variation is increased by different loadings on the godets, depending on their specific duty. Increasing godet wear will be recognized by one skilled in the art by the increase in faults (filament breakages) and there is then the additional problem of finding out which of the large number of godets in a spinning plant is causing these faults.
There has therefore been no shortage of attempts to improve the service life of thread-guiding components of spinning plants, in particular of godets. German Patent 3,218,402, for example, discloses providing thread-guiding components, such as godets or snubbing pins, with a coating of a cermet mixture containing 50-90% by weight of chromium carbide as the ceramic component and 50-10% by weight of a nickel-chromium alloy as the metal component. Compared with conventional surfaces of Al.sub.2 O.sub.3 /TiO.sub.2, this surface proves to be distinctly superior. Nonetheless, there is still room for improvement; in particular, this surface too does not make it easy to discern the state of wear.
European Patent 0 230 633 discloses providing the surface of thread-guiding components with a ceramic or metal carbide coating and draws attention in particular to tungsten carbide, but also titanium carbide, tungsten/titanium carbide and chromium carbide, alone or combined with cobalt, nickel, chromium or iron, but also to pure ceramic compositions from oxides of aluminum, aluminum/titanium, chromium, chromium/aluminum or zirconium/magnesium. To produce a defined surface quality, these layers are initially treated with an epoxy resin which closes the pores of the layer, subsequently ground to a low roughness Ra=0.2 to 0.76 .mu.m and finally provided by laser etching with a multiplicity, for example from 80 to 550, depressions per inch which have a depth from a few .mu.m to over 140 .mu.m.
It has also already been proposed to overcome the disadvantages of the state of the art by using in apparatus for producing, treating and processing fiber materials components which are characterized in that the component surface which comes into contact with the fiber material or the raw material consists of a first layer of nitrides and/or carbides of titanium or chromium deposited in a thickness from 0.1 to 10.0 .mu.m, preferably from 1 to 5 .mu.m, on a component or on a second layer of a material having a specific electric resistance of not more than 25, preferably from 20 to about 1.5 .mu..OMEGA..multidot.cm.
It is true that this measure leads to a useful improvement in the application properties of the components, but the long-term constancy of the surface properties still leaves something to be desired.